Transpiration Cooling Systems for Jet Engine Turbines and Hypersonic Flight

This grant will deliver a step change in the understanding and predictability of next generation cooling systems to enable the UK to establish a global lead in jet engine and hypersonic vehicle cooling technology. We aim to make transpiration cooling, recognised as the ultimate convective cooling system, a reality in UK produced jet engines and European hypersonic vehicles. Coolant has the potential to enable higher cycle temperatures (improving efficiency following the 2nd law of thermodynamics) but invariably introduces turbine stage losses (reducing efficiency). Cooling system improvement must enable higher Turbine Entry Temperature (TET) while using the minimum amount of coolant flow to achieve the required component life. For high speed flight, heat transfer is dominated by aerodynamic heating with gas temperatures on re-entry exceeding those at the surface of the sun. Any reduction in heat transfer to the Thermal Protection System will ultimately lead to lower mass, allowing for decreased launch costs Furthermore, the lower temperatures could serve as an enabler for higher performance technologies which are currently temperature limited. The highest temperatures achievable for both jet engines and hypersonic flight are limited by the materials and cooling technology used. The cooling benefits of transpiration flows are well established, but the application of this technology to aerospace in the UK has been prevented by the lack of suitable porous materials and the challenge of accurately modelling both the aerothermal and mechanical stress fields. Our approach will enale the coupling between the flow, thermal and stress fields to be researched simultaneously in an interdisciplinary approach which we believe is essential to arrive at the best transpiration systems. This Progreamme Grant will enable world leaders in their respective fields to work together to solve the combination of cross-disciplinary problems that arise from the application of transpiration cooling, leading to rapid innovations in this technology. The application is timely since the proposed research would enable the UK aerospace industry to capitalise on recent developments in materials, manufacturing capability, experimental facilities/measurement techniques and computational methods to develop the science for the application of transpiration cooling. The High Temperature Research Centre at Birmingham University will provide the means to cast super alloy turbine aerofoils with porosity. The proposed grant would allow innovation in the cast systems arising from combining casting expertise with aerothermal and stress modelling in recent EPSRC funded research programmes. It also builds upon material development of ultra-high temperature ceramics and carbon composites undertaken in EPSRC funded research, by use of controlled porosity and multilayer composites. It will also provide the first opportunity to undertake direct coupling of the flow with the materials (porous and non-porous) at true flight conditions and material temperatures. Recent investment in the UK's wind tunnels under the NWTF programme (EPSRC/ATI funded) at both Oxford University and at Imperial College will allow for direct replication of temperatures and heat fluxes seen in flight and interrogated using advanced laser techniques. Recent development of Fourier superposition in CFD grids for modelling film cooling can now be extended to provide a breakthrough method to predict cooling flow and metal effectiveness for high porosity/transpiration cooling systems. The European Space Agency has recently identified the pressing requirement for alternatives to one-shot ablative Thermal Protection Systems for hypersonic flight. Investment in this area is significant and transpiration cooling has been identified as a promising cooling technology. Rolls-Royce has embarked upon accelerated investment in new technologies for future jet engines including the ADVANCE